Ship some additional phpstan rules with the container

[JackNoordhuis]

The phpstan container should ship with a few of the available third party rules so plugin developers don't have to configure a composer.json just for some additional rules.

This will allow specifying the fully qualified path (will be stored somewhere like phpstan/rules) for every additional rule (may also be possible to group rules) in the phpstan.neon config.

See: https://github.com/phpstan/phpstan#extensibility (scroll down to the Unofficial extensions with third-party rules section) for some of the third party rules currently available.